Re: [RFC PATCH net-next v6 05/14] af_vsock: use a separate dgram bind table

[Amery Hung]

On Tue, Jul 23, 2024 at 7:41 AM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
>
> On Wed, Jul 10, 2024 at 09:25:46PM GMT, Amery Hung wrote:
> >From: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
> >
> >This commit adds support for bound dgram sockets to be tracked in a
> >separate bind table from connectible sockets in order to avoid address
> >collisions. With this commit, users can simultaneously bind a dgram
> >socket and connectible socket to the same CID and port.
> >
> >Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
> >---
> > net/vmw_vsock/af_vsock.c | 103 +++++++++++++++++++++++++++++----------
> > 1 file changed, 76 insertions(+), 27 deletions(-)
> >
> >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> >index d571be9cdbf0..ab08cd81720e 100644
> >--- a/net/vmw_vsock/af_vsock.c
> >+++ b/net/vmw_vsock/af_vsock.c
> >@@ -10,18 +10,23 @@
> >  * - There are two kinds of sockets: those created by user action (such as
> >  * calling socket(2)) and those created by incoming connection request packets.
> >  *
> >- * - There are two "global" tables, one for bound sockets (sockets that have
> >- * specified an address that they are responsible for) and one for connected
> >- * sockets (sockets that have established a connection with another socket).
> >- * These tables are "global" in that all sockets on the system are placed
> >- * within them. - Note, though, that the bound table contains an extra entry
> >- * for a list of unbound sockets and SOCK_DGRAM sockets will always remain in
> >- * that list. The bound table is used solely for lookup of sockets when packets
> >- * are received and that's not necessary for SOCK_DGRAM sockets since we create
> >- * a datagram handle for each and need not perform a lookup.  Keeping SOCK_DGRAM
> >- * sockets out of the bound hash buckets will reduce the chance of collisions
> >- * when looking for SOCK_STREAM sockets and prevents us from having to check the
> >- * socket type in the hash table lookups.
> >+ * - There are three "global" tables, one for bound connectible (stream /
> >+ * seqpacket) sockets, one for bound datagram sockets, and one for connected
> >+ * sockets. Bound sockets are sockets that have specified an address that
> >+ * they are responsible for. Connected sockets are sockets that have
> >+ * established a connection with another socket. These tables are "global" in
> >+ * that all sockets on the system are placed within them. - Note, though,
> >+ * that the bound tables contain an extra entry for a list of unbound
> >+ * sockets. The bound tables are used solely for lookup of sockets when packets
> >+ * are received.
> >+ *
> >+ * - There are separate bind tables for connectible and datagram sockets to avoid
> >+ * address collisions between stream/seqpacket sockets and datagram sockets.
> >+ *
> >+ * - Transports may elect to NOT use the global datagram bind table by
> >+ * implementing the ->dgram_bind() callback. If that callback is implemented,
> >+ * the global bind table is not used and the responsibility of bound datagram
> >+ * socket tracking is deferred to the transport.
> >  *
> >  * - Sockets created by user action will either be "client" sockets that
> >  * initiate a connection or "server" sockets that listen for connections; we do
> >@@ -116,6 +121,7 @@
> > static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
> > static void vsock_sk_destruct(struct sock *sk);
> > static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
> >+static bool sock_type_connectible(u16 type);
> >
> > /* Protocol family. */
> > struct proto vsock_proto = {
> >@@ -152,21 +158,25 @@ static DEFINE_MUTEX(vsock_register_mutex);
> >  * VSocket is stored in the connected hash table.
> >  *
> >  * Unbound sockets are all put on the same list attached to the end of the hash
> >- * table (vsock_unbound_sockets).  Bound sockets are added to the hash table in
> >- * the bucket that their local address hashes to (vsock_bound_sockets(addr)
> >- * represents the list that addr hashes to).
> >+ * tables (vsock_unbound_sockets/vsock_unbound_dgram_sockets).  Bound sockets
> >+ * are added to the hash table in the bucket that their local address hashes to
> >+ * (vsock_bound_sockets(addr) and vsock_bound_dgram_sockets(addr) represents
> >+ * the list that addr hashes to).
> >  *
> >- * Specifically, we initialize the vsock_bind_table array to a size of
> >- * VSOCK_HASH_SIZE + 1 so that vsock_bind_table[0] through
> >- * vsock_bind_table[VSOCK_HASH_SIZE - 1] are for bound sockets and
> >- * vsock_bind_table[VSOCK_HASH_SIZE] is for unbound sockets.  The hash function
> >- * mods with VSOCK_HASH_SIZE to ensure this.
> >+ * Specifically, taking connectible sockets as an example we initialize the
> >+ * vsock_bind_table array to a size of VSOCK_HASH_SIZE + 1 so that
> >+ * vsock_bind_table[0] through vsock_bind_table[VSOCK_HASH_SIZE - 1] are for
> >+ * bound sockets and vsock_bind_table[VSOCK_HASH_SIZE] is for unbound sockets.
> >+ * The hash function mods with VSOCK_HASH_SIZE to ensure this.
> >+ * Datagrams and vsock_dgram_bind_table operate in the same way.
> >  */
> > #define MAX_PORT_RETRIES        24
> >
> > #define VSOCK_HASH(addr)        ((addr)->svm_port % VSOCK_HASH_SIZE)
> > #define vsock_bound_sockets(addr) (&vsock_bind_table[VSOCK_HASH(addr)])
> >+#define vsock_bound_dgram_sockets(addr) (&vsock_dgram_bind_table[VSOCK_HASH(addr)])
> > #define vsock_unbound_sockets     (&vsock_bind_table[VSOCK_HASH_SIZE])
> >+#define vsock_unbound_dgram_sockets     (&vsock_dgram_bind_table[VSOCK_HASH_SIZE])
> >
> > /* XXX This can probably be implemented in a better way. */
> > #define VSOCK_CONN_HASH(src, dst)                             \
> >@@ -182,6 +192,8 @@ struct list_head vsock_connected_table[VSOCK_HASH_SIZE];
> > EXPORT_SYMBOL_GPL(vsock_connected_table);
> > DEFINE_SPINLOCK(vsock_table_lock);
> > EXPORT_SYMBOL_GPL(vsock_table_lock);
> >+static struct list_head vsock_dgram_bind_table[VSOCK_HASH_SIZE + 1];
> >+static DEFINE_SPINLOCK(vsock_dgram_table_lock);
> >
> > /* Autobind this socket to the local address if necessary. */
> > static int vsock_auto_bind(struct vsock_sock *vsk)
> >@@ -204,6 +216,9 @@ static void vsock_init_tables(void)
> >
> >       for (i = 0; i < ARRAY_SIZE(vsock_connected_table); i++)
> >               INIT_LIST_HEAD(&vsock_connected_table[i]);
> >+
> >+      for (i = 0; i < ARRAY_SIZE(vsock_dgram_bind_table); i++)
> >+              INIT_LIST_HEAD(&vsock_dgram_bind_table[i]);
> > }
> >
> > static void __vsock_insert_bound(struct list_head *list,
> >@@ -271,13 +286,28 @@ static struct sock *__vsock_find_connected_socket(struct sockaddr_vm *src,
> >       return NULL;
> > }
> >
> >-static void vsock_insert_unbound(struct vsock_sock *vsk)
> >+static void __vsock_insert_dgram_unbound(struct vsock_sock *vsk)
> >+{
> >+      spin_lock_bh(&vsock_dgram_table_lock);
> >+      __vsock_insert_bound(vsock_unbound_dgram_sockets, vsk);
> >+      spin_unlock_bh(&vsock_dgram_table_lock);
> >+}
> >+
> >+static void __vsock_insert_connectible_unbound(struct vsock_sock *vsk)
> > {
> >       spin_lock_bh(&vsock_table_lock);
> >       __vsock_insert_bound(vsock_unbound_sockets, vsk);
> >       spin_unlock_bh(&vsock_table_lock);
> > }
> >
> >+static void vsock_insert_unbound(struct vsock_sock *vsk)
> >+{
> >+      if (sock_type_connectible(sk_vsock(vsk)->sk_type))
> >+              __vsock_insert_connectible_unbound(vsk);
> >+      else
> >+              __vsock_insert_dgram_unbound(vsk);
> >+}
> >+
> > void vsock_insert_connected(struct vsock_sock *vsk)
> > {
> >       struct list_head *list = vsock_connected_sockets(
> >@@ -289,6 +319,14 @@ void vsock_insert_connected(struct vsock_sock *vsk)
> > }
> > EXPORT_SYMBOL_GPL(vsock_insert_connected);
> >
> >+static void vsock_remove_dgram_bound(struct vsock_sock *vsk)
> >+{
> >+      spin_lock_bh(&vsock_dgram_table_lock);
> >+      if (__vsock_in_bound_table(vsk))
> >+              __vsock_remove_bound(vsk);
> >+      spin_unlock_bh(&vsock_dgram_table_lock);
> >+}
> >+
> > void vsock_remove_bound(struct vsock_sock *vsk)
> > {
> >       spin_lock_bh(&vsock_table_lock);
> >@@ -340,7 +378,10 @@ EXPORT_SYMBOL_GPL(vsock_find_connected_socket);
> >
> > void vsock_remove_sock(struct vsock_sock *vsk)
> > {
> >-      vsock_remove_bound(vsk);
> >+      if (sock_type_connectible(sk_vsock(vsk)->sk_type))
> >+              vsock_remove_bound(vsk);
> >+      else
> >+              vsock_remove_dgram_bound(vsk);
>
> Can we try to be consistent, for example we have vsock_insert_unbound()
> which calls internally sock_type_connectible(), while
> vsock_remove_bound() is just for connectible sockets. It's a bit
> confusing.

I agree with you. I will make the style more consistent by keeping
vsock_insert_unbound() only work on connectible sockets.

>
> >       vsock_remove_connected(vsk);
> > }
> > EXPORT_SYMBOL_GPL(vsock_remove_sock);
> >@@ -746,11 +787,19 @@ static int __vsock_bind_connectible(struct vsock_sock *vsk,
> >       return vsock_bind_common(vsk, addr, vsock_bind_table, VSOCK_HASH_SIZE + 1);
> > }
> >
> >-static int __vsock_bind_dgram(struct vsock_sock *vsk,
> >-                            struct sockaddr_vm *addr)
> >+static int vsock_bind_dgram(struct vsock_sock *vsk,
> >+                          struct sockaddr_vm *addr)
>
> Why we are renaming this?

I will keep the original __vsock_bind_dgram() for consistency.

>
> > {
> >-      if (!vsk->transport || !vsk->transport->dgram_bind)
> >-              return -EINVAL;
> >+      if (!vsk->transport || !vsk->transport->dgram_bind) {
>
> Why this condition?
>
> Maybe a comment here is needed because I'm lost...

We currently use !vsk->transport->dgram_bind to determine if this is
VMCI dgram transport. Will add a comment explaining this.

>
> >+              int retval;
> >+
> >+              spin_lock_bh(&vsock_dgram_table_lock);
> >+              retval = vsock_bind_common(vsk, addr, vsock_dgram_bind_table,
> >+                                         VSOCK_HASH_SIZE);
>
> Should we use VSOCK_HASH_SIZE + 1 here?
>
> Using ARRAY_SIZE(x) should avoid this problem.

Yes. The size here is wrong. I will remove the size check (the
discussion is in patch 4).

Thanks,
Amery



>
>
> >+              spin_unlock_bh(&vsock_dgram_table_lock);
> >+
> >+              return retval;
> >+      }
> >
> >       return vsk->transport->dgram_bind(vsk, addr);
> > }
> >@@ -781,7 +830,7 @@ static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr)
> >               break;
> >
> >       case SOCK_DGRAM:
> >-              retval = __vsock_bind_dgram(vsk, addr);
> >+              retval = vsock_bind_dgram(vsk, addr);
> >               break;
> >
> >       default:
> >--
> >2.20.1
> >
>